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Sinnerite, Cu6As4S9, from the lengenbach quarry, Binn Valley, Switzerland: Description and re-investigation of the crystal structure


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We have characterized the crystal structure of sinnerite, Cu6As4S9, a rare sulfosalt mineral from the ores of the Lengenbach quarry, Binn Valley, Canton Valais, Switzerland, by single-crystal X-ray diffraction and chemical analysis. We found sinnerite to be structurally identical to synthetic Cu6As4S9. It is triclinic, space group P1, with cell parameters: a 9.103(2), b 9.860(3), c 9.111(2) angstrom, alpha 90.27(2), beta 109.53(2), gamma 107.58(2)degrees, V 729.6(4) angstrom(3), and Z = 2. Semi-quantitative SEM-EDS analyses confirmed the Cu6As4S9 stoichiometry. The crystal structure of an untwinned crystal has been refined to R-1 = 5.45%. It consists of a sphalerite substructure with 2/5 of the tetrahedra replaced by AsS3 pyramids; four pyramids form As4S12 clusters around the vacant anion positions of the sphalerite archetype. These pyramids are linked into twisted and branched chain-like structures with compositions As3S7 and As5S11. The chains are linked by CuS4 tetrahedra. Packing of these chains results in the OD (order-disorder) character of the sinnerite structure.
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... The Ag2 position dominated by Cu in eckerite shows a quasi-tetrahedral coordination with a mean bond distance of 2.542 Å compared to 2.674 Å in Cu-free xanthoconite (Engel and Nowacki, 1968). The ordering of copper mainly at (Karanovic et al., 2002); luzonite (Pfitzner and Bernert, 2004); sinnerite (Bindi et al., 2013)]. The shortest AgÀAg contact in the eckerite structure is Ag1ÀAg2 at 2.835 Å , slightly shorter than that found in fcc Ag metal (2.889 Å ; Suh et al., 1988). ...
Eckerite, ideally Ag 2 CuAsS 3 , is a new mineral from the Lengenbach quarry in the Binn Valley, Valais, Switzerland. It occurs as very rare euhedral crystals up to 300 μm across associated with realgar, sinnerite, hatchite, trechmannite and yellow, fibrous smithite. In thick section eckerite is opaque with a metallic lustre and shows a dark orange-red streak. It is brittle; the Vickers hardness (VHN 25 ) is 70 kg/mm ² (range: 64–78) (Mohs hardness of ∼2½–3). In reflected light, eckerite is moderately bireflectant and weakly pleochroic from light grey to a slightly bluish grey. Internal reflections are absent. Under crossed nicols, it is weakly anisotropic with greyish to light blue rotation tints. Reflectance percentages for R min and R max are 27.6, 31.7 (471.1 nm), 22.8, 26.1 (548.3 nm), 21.5, 24.5 (586.6 nm) and 19.4, 22.3 (652.3 nm), respectively. Eckerite is monoclinic, space group C 2/ c , with a = 11.8643(3), b = 6.2338(1), c = 16.6785(4) Å, β = 110.842(3)°, V = 1152.81(5) Å ³ , Z = 8. The crystal structure [ R 1 = 0.0769 for 1606 reflections with F o > 4σ( F o )] is topologically identical to that of xanthoconite and pyrostilpnite. In the structure, AsS3 pyramids are joined by AgS 3 triangles to form double sheets parallel to (001); the sheets are linked by Cu(Ag) atoms in a quasi-tetrahedral coordination. Among the three metals sites, Ag2 is dominated by Cu. The mean metal–S distances reflect well the Ag ↔ Cu substitution occurring at this site. The eight strongest powder X-ray diffraction lines [ d in Å ( I / I 0 ) (hkl)] are: 3.336 (70) (312); 2.941 (100) (314,114); 2.776 (80) (400,206); 2.677 (40) (312); 2.134 (50) (421); 2.084 (40) (208,206); 2.076 (40) (420); 1.738 (40) (228,226). A mean of five electron microprobe analyses gave Ag 52.08(16), Cu 11.18(9), Pb 0.04(1), Sb 0.29(3), As 15.28(11), S 20.73(13), total 99.60 wt.%, corresponding, on the basis of a total of 7 atoms per formula unit, to Ag 2.24 Cu 0.82 As 0.94 Sb 0.01 S 2.99 . The new mineral has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (2014–063) and named for Markus Ecker, a well known mineral expert on the Lengenbach minerals for more than 25 years.
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Tennantite-(Hg), Cu 6 (Cu 4 Hg 2 )As 4 S 13 , was approved as a new mineral species (IMA2020-063) from the Lengenbach quarry, Imfeld, Binn Valley, Canton Valais, Switzerland. It was identified as an aggregate of black metallic tetrahedral crystals, less than 0.1 mm in size, intimately associated with sinnerite, and grown on realgar. In reflected light, tennantite-(Hg) is isotropic, grey in colour, with creamy tints. Minimum and maximum reflectance data for COM wavelengths in air are [λ (nm): R (%)]: 470: 29.1; 546: 29.1; 589: 28.5; 650: 27.7. Electron microprobe analysis gave (in wt.% – average of 7 spot analyses): Cu 32.57(42), Ag 6.38(19), Tl 0.29(14), Zn 0.04(5), Hg 17.94(2.27), Pb 0.70(51), As 17.83(61), Sb 0.34(8), S 24.10(41), total 100.19(1.04). The empirical formula of the sample studied, recalculated on the basis of Σ Me = 16 atoms per formula unit, is (Cu 4.69 Ag 1.04 Tl 0.03 ) Σ5.76 (Cu 4.35 Hg 1.58 Pb 0.06 Zn 0.01 ) Σ6.00 (As 4.20 Sb 0.05 ) Σ4.25 S 13.26 . Tennantite-(Hg) is cubic, I $\overline 4$ 3 m , with a = 10.455(7) Å, V = 1143(2) Å ³ and Z = 2. The crystal structure of tennantite-(Hg) has been refined by single-crystal X-ray diffraction data to a final R 1 = 0.0897 on the basis of 214 unique reflections with F o > 4σ( F o ) and 22 refined parameters. Tennantite-(Hg) is isotypic with other members of the tetrahedrite group. Mercury is hosted at the tetrahedrally coordinated M (1) site, in accord with the relatively long M (1)–S(1) distance (2.389 Å), similar to that observed in tetrahedrite-(Hg). Minor Ag is located at the triangularly-coordinated and split M (2) site. Other occurrences of tennantite-(Hg) are briefly reviewed and the Lengenbach finding is described within the framework of previous knowledge about the Hg mineralogy at this locality.
Sinnerite (Cu6As4S9) is a semiconductor computed to have attractive optoelectronic properties, but little attention has been paid to its experimental synthesis and characterization. Here, the authors report the first synthesis of polycrystalline sinnerite thin films. By heating Cu3AsS4 nanoparticles in sealed ampoules with As2S2 powder, a phase transformation to Cu6As4S9 is achieved along with the formation of micronsized dense grains appropriate for device applications. The films display a bandgap of ~1.2 eV, significant photocurrent generation under simulated AM1.5 illumination, and carrier lifetimes nearing 1 ns, demonstrating the promise of sinnerite for use in photovoltaic applications.
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Complex sulfides of thallium with As, Sb, or Bi and with other cations (‘thallium sulfosalts’) are a large group of crystal structures with extreme variability. Incorporation of the large Tl+ cation in them is solved in several different ways: housing of Tl in columns of capped trigonal coordination prisms, which form separate walls in the structure (in different combinations with Pb and/or Sb), regular alternation of large Tl with small cations (As), presence of structural arrays of Tl coordination polyhedra paralleled by arrays of As coordination pyramids with a frequency ratio 1:2, omission derivatives with cavities for Tl accommodation and formation of layer structures with thallium concentrated into separate (inter)layers of different types. The first principle leads to a large family of sartorite homologues and rare lillianite homologues, as well as to the chabournéite group. The second one to the hutchinsonite family, omission derivatives form the routhierite and galkhaite groups, and the 1:2 periodicity ratio principle results in several outstanding structures from different groups. Layer structures consist of two-component and three-component layer combinations. Close cation-cation interactions are present but rare.
Bond-valence parameters which relate bond valences and bond lengths have been derived for a large number of bonds. It is shown that there is a strong linear correlation between the parameters for bonds from cations to pairs of anions. This correlation is used to develop an interpolation scheme that allows the estimation of bond-valence parameters for 969 pairs of atoms. A complete listing of these parameters is given.
Ternary phases in the system Cu-As-S are luzonite, enargite, tennantite, lautite (CuAsS), sinnerite (Cu 6 As 4 S 9 ) and a new compound A (Cu 24 As 12 S 31 ). The only compound to have an extensive composition field is tennantite, for which the generalized formula Cu (sub 12+x) As (sub 4+y) S 13 is proposed, where 0 < or =x< or =1.72 and 0 < or =y< or =0.08. Down to 300 degrees C the lowest temperature studied, the temperature sensitive composition field for tennantite does not reach the generally accepted composition Cu 12 As 4 S 13 . It is highly probable that this composition is reached at lower temperatures.Phase relations are dominated by the join Cu 2 S-As, which remains stable from the liquidus down to at least 300 degrees C and precludes the stable coexistence of the copper arsenides with ternary compounds, and by the expansion of a liquid field from the As-S sideline into the ternary. Interactions between the solids, and the liquidus relations occasioned by the expanding liquid field, lead to a series of reaction points of interest in the studies of ore deposits.
An account is given of the development of the SHELX system of computer programs from SHELX-76 to the present day. In addition to identifying useful innovations that have come into general use through their implementation in SHELX, a critical analysis is presented of the less-successful features, missed opportunities and desirable improvements for future releases of the software. An attempt is made to understand how a program originally designed for photographic intensity data, punched cards and computers over 10000 times slower than an average modern personal computer has managed to survive for so long. SHELXL is the most widely used program for small-molecule refinement and SHELXS and SHELXD are often employed for structure solution despite the availability of objectively superior programs. SHELXL also finds a niche for the refinement of macromolecules against high-resolution or twinned data; SHELXPRO acts as an interface for macromolecular applications. SHELXC, SHELXD and SHELXE are proving useful for the experimental phasing of macromolecules, especially because they are fast and robust and so are often employed in pipelines for high-throughput phasing. This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination.
Faszination Lengenbach Abbau-ForschungMineralien International Tables for X-ray Crystallography The Netherlands
As6-S1 2.33(3) Cu8-S3 2.28(3) As6-S7 2.40(3) Cu8-S4 2.31(2) As6-S11 2.54(3) Cu8-S12 2.34(3) Cu8-S10 2.45(3) As7-S10 2.27(3) As7-S5 2.30(3) Cu9-S9 2.20(3) As7-S18 2.36(3) Cu9-S4 2.24(3) Cu9-S2 2.31(3) As8-S4 2.20(3) Cu9-S13 2.36(3) As8-S14 2.25(3) As8-S8 2.34(3) Cu10-S5 2.22(3) Cu10-S11 2.38(3) Cu1-S16 2.20(3) Cu10-S4 2.42(3) Cu1-S6 2.27(3) Cu10-S17 2.40(3) Cu1-S18 2.30(3) Cu1-S14 2.47(3) Cu11-S9 2.16(3) Cu11-S18 2.20(3) Cu2-S18 2.29(3) Cu11-S17 2.21(3) Cu2-S15 2.34(3) Cu11-S3 2.33(3) Cu2-S1 2.39(3) Cu2-S12 2.44(3) Cu12-S3 2.11(3) Cu12-S15 2.22(3) Cu3-S1 2.15(3) Cu12-S7 2.28(3) Cu3-S14 2.30(3) Cu12-S16 2.33(3) Cu3-S17 2.31(3) Cu3-S2 2.47(3) graEsEr, s., cannon, r., drEchsLEr, E., rabEr, t., & roth, p. (2008) Faszination Lengenbach Abbau-ForschungMineralien 1958-2008. Kristallographik Verlag, Achberg, 192p. ibErs, J.a. & hamiLton, w.c., Eds. (1974) International Tables for X-ray Crystallography, Volume IV. Kynoch Press, Dordrecht, The Netherlands, 366p.
Studies of the sulfosalts of copper. II. The crystallography and composition of sinnerite, Cu 6 As 4 S 9
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  • B J Skinner
makovicky, E. & skinnEr, b.J. (1972) Studies of the sulfosalts of copper. II. The crystallography and composition of sinnerite, Cu 6 As 4 S 9. American Mineralogist 57, 824-834.
Faszination Lengenbach Abbau-Forschung-Mineralien
  • S Graeser
  • Cannon
  • E Drechsler
  • P Roth
graEsEr, s., cannon, r., drEchsLEr, E., rabEr, t., & roth, p. (2008) Faszination Lengenbach Abbau-Forschung-Mineralien 1958-2008. Kristallographik Verlag, Achberg, 192p. ibErs, J.a. & hamiLton, w.c., Eds. (1974) International Tables for X-ray Crystallography, Volume IV. Kynoch Press, Dordrecht, The Netherlands, 366p.